The present invention relates to a rotor of rotary machines and to a method of making the same, and more specifically to a rotor in which a core member is composed of a plurality of hollow members so as to be suited for rotary machines such as a-c generators of automobiles and to a method of making the same.
Conventional technique for fastening a rotary shaft to a core member which constitutes a rotor of a rotary machine has heretofore been relying upon a method of forcibly inserting the core member into the knurled rotary shaft to ensure very large fastening force. According to the above method, however, a great force of an axial direction is exerted on the rotary shaft when it is being inserted; the rotary shaft tends to be bent. The rotary shaft which is bent causes the life of the rotary machines to be shortened or produces noise.
Besides, the core member is not often sufficiently fitted to the knurled portion and fails to ensure great mechanically coupled force (rotational torque).
Furthermore, shear bursting force is small with respect to the stress in the axial direction.
Another fastening method consists of knurling the rotary shaft like the above-mentioned method, forming an annular groove in the rotary shaft at a position corresponding to an end surface of the rotor core, forcibly introducing the rotor core and yoke into the rotary shaft, and coining the end portion of the rotor core so that they are prevented from being removed in the axial direction. With this method, the force against the stress in the axial direction can be improved to some extent, which, however, is not still sufficient.